Guest Stars Belinda Lang as Mrs Clam David Sterne as Tom Thomas Robert Daws as CC Lowsley Jack Gouldbourne as Norman Whalley Mat Fraser as Clement Rugg John Hollingworth as Trevor Symonds Penny Ryder as Myrtle Hunnisweet Lisa Allen as Irene Symonds Juliet Oldfield as Brenda Bristow Mark Donald as Bletchley Park Supervisor Robert Maskell as Oswald Blower